|Publication number||US5329681 A|
|Application number||US 07/706,643|
|Publication date||Jul 19, 1994|
|Filing date||May 29, 1991|
|Priority date||Jun 15, 1990|
|Also published as||CA2044648A1, DE4019256A1, EP0464397A1, EP0464397B1|
|Publication number||07706643, 706643, US 5329681 A, US 5329681A, US-A-5329681, US5329681 A, US5329681A|
|Original Assignee||Varta Batterie Aktiengesellschaft|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (14), Referenced by (1), Classifications (7), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This invention relates to the electrical and mechanical connection of a metal strip which serves as the current take-off to an electrode of a galvanic element having a porous metallic framework as its carrier.
The trouble-free attachment of the current take-off to a battery electrode requires that the metallic carrier portion of the electrode have, at the intended attachment point, a metallic portion which is freely accessible and which is not contaminated by the electrode-active material. This serves to keep the contact resistance developed across the subsequent spot weld as low as possible. In ultrasonic welding, a clean contact surface is required for higher performance values.
From German Patent Publication (DE-AS) 2,211,233, for example, it is known to uniformly coat a tape-like wire mesh made of nickel, nickel plated iron, or copper, with a powdered active mass. Flat pieces are then cut from the coated web, and are reinforced by straight-bending at their edges. Current take-offs are then welded to these cut segments, at discrete points along the reinforced edges, following removal of the compressed active material. However, removal of the active mass is difficult, and often incomplete.
In the production of sinter foil electrodes, a solid metal edge of the center web, to which a current take-off may be welded, is customarily excluded (isolated) from impregnation with the electrode active material. However, in order to isolate this edge, suitable precautions must be taken during application of the porous nickel sinter layers to the foil carrier web. This requires additional effort, as compared to a uniform processing of the carrier web.
According to German Patent (DE-PS) 2,535,469, it is possible to weld a metallic take-off conductor directly to a sinter foil electrode if the active material which is embedded in its porous electrode framework, e.g., nickel hydroxide, is first reduced at the desired attachment point by dripping a solution of hydrazine hydrate or sodium borate onto the metal. For rechargeable battery systems, electrodes based upon porous metallic frameworks have been used as carriers and current collectors.
These tape-like porous structures (produced galvanically) can easily be filled with active mass due to their high porosity (i.e., 95 to 97%) through soaking or pasting, and are particularly suited to the production of wound electrodes. The attachment of take-off conductors takes place, for example, by sealing and gluing closed the selected attachment points, even before application of the active mass. The carrier web is then impregnated with the active mass, dried and rolled. Following removal of the protective mass, the take-off conductors are welded at the desired attachment points, which are then free of the pasted or suspended mass.
This procedure is complicated, and rather impractical, because such manufactured webs tend to experience a change in length during post-rolling to their desired final thickness, which can be as much as 20%. As a result, the ultimate locations of the attachment points cannot be precisely determined, and a certain variation in location must therefore be taken into account during subsequent stamping or separating of the electrode strips.
It is therefore the objective of this invention to provide a pre-treatment of finished porous metallic framework electrodes before attachment (by welding) of the take-off conductors, to ensure a clean and homogenous connection.
This object, and others which will appear, are achieved in accordance with the present invention by heating and then air-blasting the surface of a porous metallic framework carrier or plate made of a sponge-like metal matrix (metal foam) as disclosed in U.S. Pat. No. 4,251,603 at the intended point of attachment for the take-off conductor, prior to welding the take-off conductor to the carrier.
In accordance with the present invention, the intended contact location of a porous metallic carrier is first subjected to heating. This alters (decomposes) active material contained within the pores of the metallic framework, so that the active material can then be expelled with a jet of air.
Because the active mass which is pasted or soaked into the porous metallic framework normally contains an organic binder, it is in principle the destruction by heat of this organic substance (in addition to moisture) which deprives the active material of its ability to adhere to the walls of the pores. As a result, after being heated the active material behaves like a dry powder and can then be readily blown from the pores by a stream of gas under pressure; in particular, a stream of compressed air.
A variety of heat sources may be used to accomplish this thermal decomposition. For example, a heated die, a laser beam, or induction heating may be used. In any event, the required temperature, depending upon the resistance to heat of the binder material to be removed, should be in a range of from about 300° C. to 550° C.
It is particularly advantageous to direct a stream of hot air at a temperature which lies in the above-mentioned range, and preferably at about 450°, upon the location to be prepared before the area to be cleared of all non-metallic residues is subjected to the stream of compressed air. For a reliable removal of residues, stream pressures of from about 7 to 8 bar are necessary, with the compressed gas preferably issuing from a small nozzle. The resulting gas flow is too high for simultaneous use as both the source of heat (for achieving the desired thermal decomposition) and the compressed air stream, because the amount of energy which would be necessary to heat such quantities of air to the desired temperature (e.g., to about 450) would not be economical. Conversely, the hot air stream which is used to heat the surface would be too weak to also serve as the compressed air stream. As a consequence, a two-stage procedure is preferred.
It is further advantageous to cover the electrode web with an effective heat conducting metal sheet (e.g., a copper sheet), and to stamp from this the desired application point for the take-off conductor. This serves to concentrate the heat upon the attachment surface, which approximates the outline of the take-off conductor strip, and which is necessary for the welded connection.
Under such conditions, the binder material is generally decomposed within about 3 to 12 seconds, and in most cases within 5 to 7 seconds, without the occurrence of any significant oxidation of the carrier metal in this region.
The disclosed concentrated heating effect is further advantageously accomplished from both sides of the carrier, by directing a hot air stream from both sides upon the contact location. After the binder material of the active mass has been destroyed, the treated location can then readily be blown free of active mass with compressed air, or with a blower, as previously described. In any event, the basis (surface) for a trouble-free welded connection with the take-off conductor results.
The particular advantage of the procedure of the present invention, from a manufacturing standpoint, is that the attachment of the take-off conductor takes place only after the carrier web has been subjected to all of the treatments associated with mass impregnation, including post-rolling and drying, so that exposed attachment points are not subjected to rollers, guides and the like, which could compromise the web, or which could themselves be damaged during such transport. The locations of the contact points which need to be cleared of active material (upon the electrode web) can then be precisely located, in their desired distribution. It is still further advantageous to treat electrodes in accordance with the process of this invention, after they have been cut to their final dimensions. In such case, only that small segment of the electrode surface which is needed for welded connection with the take-off conductor is effected by the treatment of the present invention.
It will be understood that various changes in the details, materials and arrangement of parts which have been herein described and illustrated in order to explain the nature of this invention may be made by those skilled in the art within the principle and scope of the invention as expressed in the following claims.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US1940385 *||Jul 11, 1931||Dec 19, 1933||Ig Farbenindustrie Ag||Electrode for accumulators|
|US1988861 *||Feb 18, 1930||Jan 22, 1935||Ig Farbenindustrie Ag||Production of metallic plates suitable for use as accumulator electrodes|
|US2544112 *||Jan 5, 1949||Mar 6, 1951||Accumulatoren Fabriek Varta N||Sintered battery plate and process of making|
|US2724733 *||Nov 1, 1952||Nov 22, 1955||Peters Freimut||Alkaline storage battery electrodes|
|US4251603 *||Feb 13, 1980||Feb 17, 1981||Matsushita Electric Industrial Co., Ltd.||Battery electrode|
|US5154993 *||Apr 27, 1990||Oct 13, 1992||Eveready Battery Company, Inc.||Electrode strips for coiled assemblies and method of producing them|
|US5196281 *||Sep 20, 1990||Mar 23, 1993||Gates Energy Products, Inc.||Electrode having a conductive contact area and method of making the same|
|CA589193A *||Dec 22, 1959||Accumulatoren Fabrik Ag||Alkaline electric accumulator|
|DE2211233A1 *||Mar 8, 1972||Sep 28, 1972||Svenska Ackumulator Ab||Title not available|
|DE2327885A1 *||Jun 1, 1973||Dec 19, 1974||Deutsche Automobilgesellsch||Verfahren zur herstellung eines elektrodengeruestes fuer elektroden in galvanischen elementen|
|DE2427421A1 *||Jun 5, 1974||Jan 9, 1975||Battelle Memorial Institute||Verfahren zur herstellung einer positiven nickel-hydroxid-elektrode fuer galvanische zellen|
|DE2427422A1 *||Jun 5, 1974||Jan 9, 1975||Battelle Memorial Institute||Verfahren zur herstellung einer positiven nickel-hydroxid-elektrode fuer galvanische zellen|
|DE2535469A1 *||Aug 8, 1975||Feb 24, 1977||Varta Batterie||Verfahren zur elektrischen und mechanischen verbindung eines als ableiter dienenden metallstreifens mit einer aktive masse enthaltenden poroesen elektrode fuer galvianische elemente|
|JPS60170166A *||Title not available|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US6298530||Jun 8, 2000||Oct 9, 2001||Duracell Inc.||Reinforced coiled electrode assemblies and methods of producing same|
|U.S. Classification||29/2, 429/235, 429/237|
|Cooperative Classification||Y10T29/10, H01M2/26|
|Jul 15, 1991||AS||Assignment|
Owner name: VARTA BATTERIE AKTIENGESELLSCHAFT A CORP. OF FED
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:SAUER, HANS;REEL/FRAME:005771/0835
Effective date: 19910605
|Jan 12, 1998||FPAY||Fee payment|
Year of fee payment: 4
|Feb 13, 2002||REMI||Maintenance fee reminder mailed|
|Jul 19, 2002||LAPS||Lapse for failure to pay maintenance fees|
|Sep 17, 2002||FP||Expired due to failure to pay maintenance fee|
Effective date: 20020719